Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Boeing Model 747 airplanes. The existing AD currently requires inspections to detect disbonding, corrosion, and cracking at the longitudinal rows of fasteners in the bonded skin panels in section 41 of the fuselage, and repair, if necessary. This proposed AD would add airplanes to the applicability, and require new inspections of airplanes that may have Alodine-coated rivets installed. This proposed AD results from a report of cracking discovered in a skin lap joint that was previously inspected using the eddy current method. We are proposing this AD to prevent rapid decompression of the airplane due to disbonding and subsequent cracking of the skin panels.